I could probably answer this question myself after learning enough Scheme, but I'm using iOS Gambit REPL to learn Scheme and need to know one thing to help me get started:
How can one retrieve a saved file and edit it?
I was able to figure out how to use the editor to create a working program, and to save it, to load it into the REPL to run it, and to print a list of the files in the user directory. But, if I save a file, then delete its editor window, there doesn't seem to be a way to bring it back for further editing. I think this would be rather important for writing and refining reusable modules and code snippets, and for working with the rather large initialization files used by Scheme textbooks, etc.
Hopefully this doesn't require a new feature and therefore a new release to the App Store. If it does, then another desirable feature would be to implement the "Open In..." hooks so one could use an advanced editor like Textastic with Gambit REPL.
By the way, thank you for creating the app in the first place - it will introduce Scheme to a broader community. It's elegant and even looks beautiful.
I'd be happy to document the iOS specifics (such as the answer to this question) on the Wiki.
Ed